Optical display unit, and sheet material and roll for use therein

ABSTRACT

A material roll including a roll of a continuous sheet material, including an optical member including a polarizer and a release film provided on one side of the optical member with an adhesive interposed therebetween, wherein when no external force is applied, the continuous sheet material curls in the longitudinal direction in such a way that the release film is facing inward, and the continuous sheet material is for use in a process including bonding the optical member to a substrate with the adhesive interposed therebetween to form an optical display unit.

CROSS-REFERENCE OF RELATED APPLICATIONS

This application is a Divisional of application Ser. No. 12/745,428,filed May 28, 2010, which is a 371 of International Application No.PCT/JP2008/071890 filed Dec. 2, 2008.

TECHNICAL FIELD

The invention relates to a method for manufacturing an optical displayunit including a substrate and an optical member that includes apolarizer and is bonded to the substrate with an adhesive interposedtherebetween. The invention also relates to a sheet material and amaterial roll thereof for use in the optical display unit manufacturingmethod.

BACKGROUND ART

FIG. 18 schematically shows a conventional method for manufacturing anoptical display unit to be incorporated into a liquid crystal displaydevice. First, an optical film manufacturer produces a continuous sheetmaterial, which includes an optical member, in the form of a materialroll (#1). Examples of the “continuous sheet material” include a rawpolarizing plate, a raw laminated film of a polarizing plate and aretardation plate, and so on for use in the production of liquid crystaldisplays. The material roll is then slit into a predetermined size (asize according to the size of a substrate) (#2). The slit piece of thecontinuous material is then cut into a specific length according to thesize of the substrate to be bonded (#3). The specific-length piece ofthe sheet material is then subjected to an appearance inspection (#4).The finished product is then inspected (#5). Subsequently, the four endfaces of the piece of the sheet material are worked (#6). The working isperformed to prevent the adhesive or the like from coming out of the endfaces in transit. The piece of the sheet material is then subjected toclean packaging in a clean room environment (#7). Subsequently,packaging for transportation (transport packaging) is performed (#8).The piece of the sheet material manufactured as described above istransported to a panel processing manufacturer.

The panel processing manufacturer unpacks the piece of the materialsheet transported (#11). An appearance inspection is then performed tocheck whether scratches, stains or other defects are produced in transitor during unpacking (#12). The piece of the sheet material determined asnon-defective in the inspection is then transferred to the next step.This appearance inspection may be omitted in some cases. The substrate(such as a glass substrate with a sealed liquid crystal cell) to whichthe piece of the sheet material will be bonded is previouslymanufactured and cleaned before the bonding step (#13).

The piece of the sheet material and the substrate are bonded together toform an optical display unit (#14). The release film is peeled off fromthe piece of the sheet material so that the adhesive can be left, andone side of the substrate is bonded to the surface of the adhesive. Theother side of the substrate may also be bonded in a similar manner. Abonded state inspection and a defect inspection are then performed(#15). The optical display unit determined as non-defective in theinspection is transferred to an implementing step and implemented into aliquid crystal display device (#16). On the other hand, the opticaldisplay unit determined as defective is subjected to a reworking process(#17). In the reworking process, the optical member is peeled off fromthe substrate. A new optical member is bonded to the reworked substrate(#14).

The manufacturing process described above particularly requires thesteps of working the end faces, packaging the piece of the sheetmaterial, and unpacking the material, because the optical filmmanufacturer and the panel processing manufacturer are located atdifferent places. However, such a multi-step process has the problem ofan increase in manufacturing cost. There are also problems in whichscratches, dust, stains, and so on can be caused by the multi-stepprocess or the transportation so that an inspection process can benecessary, and problems in which different types of sheet materials mustbe carried and managed.

Japanese Patent Application Laid-Open (JP-A) No. 2007-140046 (PatentLiterature 1) discloses a method for solving the problems. According tothe publication, a sheet material including an optical member is drawnfrom a roll thereof, and whether the sheet material has any defect isdetected. Based on the result of the detection, the sheet material iscut into pieces. Subsequently, the release film is peeled off, and thenthe cut piece of the sheet material is bonded to a liquid crystal cellsubstrate. The above steps are arranged in a continuous manufacturingline. Therefore, a roll of the sheet material can be directly packagedand delivered, in contrast to the conventional method including stampingthe sheet material into pieces, carefully packaging each piece of thesheet material after the stamping, and delivering it to a panelprocessing manufacturer. JP-A No. 2005-37416 (Patent Literature 2)proposes another continuous manufacturing method including cutting themembers (e.g., a polarizing plate) of a sheet material other than arelease film so that the sheet material can be kept continuous by meansof the release film and bonding the cut piece of the sheet material to asubstrate with the adhesive interposed therebetween, while peeling offthe release film.

-   Patent Literature 1: Japanese Patent Application Laid-Open (JP-A)    No. 2007-140046.-   Patent Literature 2: Japanese Patent Application Laid-Open (JP-A)    No. 2005-37416.

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

The continuous manufacturing method has a problem in which the othermembers peel from the release film in a certain feed route after thecutting, so that feed trouble or degradation of the accuracy of bondingto the substrate may occur. In particular, as shown in Parts (a) and (b)of FIG. 19, a peeling accident in which an edge of a member F peels froma release film H is more likely to occur, when the release film H andthe member F of a cut piece of the sheet material are turned back at anangle of 90 to 180 degrees on a roller R. If the peeling member F istransported as it is, it may adhere to a surrounding to cause feedtrouble. If the peeling member F is bonded to the substrate, a reductionin the bonding accuracy may occur. Hereinafter, a process includingcutting the members of the sheet material other than the release film orthe surface protecting member, while leaving the release film or thesurface protecting member uncut may be called “half cutting,” and aprocess including bonding a carrier film to the sheet material andcutting the sheet material while leaving the carrier film uncut may alsobe called “half cutting.”

The invention has been made in view of the above circumstances, and anobject of the invention is to provide an optical display unitmanufacturing method that includes subjecting a sheet material havingcurling properties to half cutting and bonding the cut piece of thesheet material to a substrate with an adhesive interposed therebetween,while peeling off the member left uncut and can solve the problem ofpeeling of the cut piece of the sheet material during feeding after thehalf cutting in such a process, so that the cut piece of the sheetmaterial can be bonded to the substrate in a satisfactory manner.Another object of the invention is to provide a sheet material and aroll thereof for use in such an optical display unit manufacturingmethod.

Means for Solving the Problems

As a result of investigations to solve the above problems, the inventiondescribed below has been accomplished.

The invention is directed to a continuous sheet material, including:

an optical member including a polarizer; and

a release film provided on one side of the optical member with anadhesive interposed therebetween, wherein

when no external force is applied, the continuous sheet material curlsin the continuous itudinal direction in such a way that the release filmis facing inward, and

the continuous sheet material is for use in a process including bondingthe optical member to a substrate with the adhesive interposedtherebetween to form an optical display unit.

This feature is effective and advantageous as described below. Thecontinuous sheet material is suitable for use in a process includingbonding the optical member including a polarizer to a substrate with theadhesive interposed therebetween to form an optical display unit. Thesheet material includes at least the optical member and the release filmprovided on one side of the optical member with the adhesive interposedtherebetween. The sheet material may further include, as a component, asurface protecting member provided on the opposite side from the releasefilm side. When no external force is applied, the sheet material curlsin the longitudinal direction in such a way that the release film isfacing inward. The term “external force” typically means a tensileforce, a pressure, or any other external force other than gravity. Sincethe sheet material is formed in such a way that the release film cancurl inward, the member having undergone half cutting is well preventedfrom peeling from the release film. Therefore, for example, when placedon the roller R as shown in FIG. 19, the member having undergone halfcutting is well prevented from the peeling phenomenon in which themember peels from the release film, so that the accuracy of bonding ofthe member to the substrate is improved. The method for manufacturingthe optical display unit is described in detail below. The curlingproperties of the sheet material are caused by part or all of thefactors derived from the components of the sheet material. For example,the curling properties may be caused by a structure composed of thepolarizer, which forms the optical member, and a film member provided onat least one side of the polarizer. In an embodiment of the invention,the state of “curling” is intended to include not only a state in whichthe curling surface has the same radius of curvature but also a state inwhich the curling surface has portions with different radii ofcurvature.

In an embodiment of the invention, a cut sample of the sheet materialpreferably has a curling amount of 5 mm to 100 mm, when it is placed ona flat surface so that it can curl to become convex downwardly, whereinthe sample is obtained by cutting the sheet material in a length of 29.7cm parallel to the longitudinal direction and in a width of 21.0 cmperpendicular to the longitudinal direction, and the curling amount isthe height of an edge of the sample from the flat surface. The curlingamount is preferably from 10 mm to 80 mm.

The curling amount may be evaluated by the curling amount measuringmethod described below. As shown in FIGS. 13 and 14, the continuoussheet material composed of various components is fed and cut in a sizeof 29.7 cm (parallel to the feeding direction (longitudinal direction:MD)) and in a size of 21.0 cm (parallel to the direction (transversedirection: TD) perpendicular to the feeding direction), so that thesample to be used is obtained. The measurement is performed in anenvironment at a temperature of 23° C. and a humidity of 55% RH. Thesample is allowed to stand for about 10 seconds, and the curlingdirection is confirmed. After the curling direction is confirmed, thesample is placed, as shown in FIG. 13, on a flat surface plate so thatit can curl to become convex downwardly when viewed from the side. After10 minutes, the height (h) of an upper edge of the curling sample fromthe upper surface of the flat surface plate is measured. The height (h)is used as the amount of curling. The measurement is performed by visualobservation using a stainless steel ruler (or a digital verniercaliper). The state in which the sheet material curls so that therelease film is facing inward is named “minus curling.” On the otherhand, the state in which the sheet material curls so that the releasefilm is facing outward is named “plus curling.” FIG. 14 shows an exampleof the structure of the sample subjected to the measurement of theamount of curling. The example of the sheet material of the inventioncurls in the longitudinal direction so that the release film is facinginward (a minus curling sheet material). Another sheet material curls sothat the release film is facing outward (a plus curling sheet material).In FIG. 14, the stretched PVA has the specifications shown in Table 1.TAC2 is TD-80UL manufactured by Fujifilm Corporation. PET (polyethyleneterephthalate) is manufactured by Mitsubishi Polyester Film Corporation.The surface protecting film (an example of the surface protectingmember) is a polyethylene terephthalate film with a thickness of 38 μm.The adhesive on the surface protecting film side is an acrylic adhesivewith a layer thickness of about 20 μm. The release film is apolyethylene terephthalate film with a thickness of 25 μm.

When the amount of curling is 5 mm or more in the minus curlingdirection, the process of feeding the sheet material having undergonehalf cutting can be free from a problem such as peeling of the cut pieceof the sheet material member (e.g., the optical member) from the releasefilm. If the amount of curling is more than 100 mm in the minus curlingdirection, the accuracy of bonding of the cut piece of the sheetmaterial member to the substrate may be undesirably reduced.

The optical member is not restricted, and examples thereof includevarious combinations of components as described below.

In an embodiment of the invention, the sheet material may be wound sothat the release film is placed inside.

When the sheet material is wound so that the release film is placedinside according to this feature, the sheet material is caused to have acurling habit, so that the sheet material with no external force appliedthereto curls with the release film facing inward. According to theinvention, peeling of the cut piece of the member during feeding and theproblem with the accuracy of bonding to the substrate are prevented.

In an embodiment of the invention, the optical member may include afirst film provided on one side of the polarizer, a second film providedon the other side of the polarizer, and an adhesive provided on thesecond film, wherein

the release film is provided on the second film with the adhesiveinterposed therebetween, and

the longitudinal dimensional change rate of the first film is lower thanthe longitudinal dimensional change rate of the second film.

According to this feature, the optical member includes the polarizer,the first and second films provided on both sides of the polarizer andhaving different longitudinal dimensional change rates, and the adhesiveprovided on the second film. For example, the first and second films mayeach form a polarizer protecting film. The release film is provided onthe second film with the adhesive interposed therebetween. The effect ofthe dimensional changes of the polarizer itself and the first and secondfilms having different dimensional change rates allows the opticalmember itself to curl, so that the sheet material curls with the releasefilm facing inward. In some cases, the curling properties of the wholeof the sheet material may be influenced by not only the properties ofthe optical member but also the properties of the release film or anyother member.

A method for measuring the “dimensional change rate (%, at 70° C.)” isdescribed below. For the measurement of the dimensional change rate inthe longitudinal direction (feed direction), a sample strip is preparedthat is 10 mm long in the feed direction (MD) and 3 mm long in adirection perpendicular thereto. For the measurement of the dimensionalchange rate in the direction perpendicular to the feed direction, asample strip is prepared that is 10 mm long in the directionperpendicular to the feed direction (also referred to as TD) and 3 mmlong in the feed direction (MD). The dimensional change rate is measuredat 70° C. using TMA/SS6100 manufactured by Seiko Instruments Inc. Themeasurement conditions are as follows. The sample strip is cooled at arate of 10° C./minute from room temperature to −50° C. and then held at−50° C. for 30 minutes. Subsequently, the sample strip is heated at arate of 10° C./minute to 100° C. and then held at 100° C. for 30minutes. Three cycles of this process are performed. After the threecycles, the dimensional change rate is determined using TMA/SS6100.After two cycles of the process, the resulting data is used to evaluatethe dimensional change rate. The evaluation is calculated by dividingthe amount of dimensional change at 70° C. by 10,000 and multiplying theresult by 100 ({(the amount of dimensional change at 70°C.)/10,000}×100).

In another embodiment of the invention, the continuous sheet materialmay be wound into a roll. The material roll is preferably used in amethod for manufacturing an optical display unit as described below.

The invention is also directed to a method for manufacturing an opticaldisplay unit including a substrate and an optical member that includes apolarizer and is bonded to the substrate with an adhesive interposedtherebetween, which includes:

a cutting step including feeding a continuous sheet material from a rollof the continuous sheet material, wherein the continuous sheet materialincludes the optical member and a release film provided on one side ofthe optical member with the adhesive interposed therebetween, andcutting the sheet material by cutting means, while leaving the releasefilm uncut; and

a bonding step including bonding the sheet material to the substratewith the adhesive interposed therebetween, while removing the releasefilm, wherein

when no external force is applied, the sheet material curls in thelongitudinal direction so that the release film is facing inward.

This feature is effective and advantageous as described below. First,the continuous sheet material is provided in the form of a roll. Thesheet material includes at least an optical member and a release filmand typically further includes a peelable surface protecting memberprovided on the surface of the optical member.

The optical member may include at least a polarizer and a polarizerprotecting film. Examples of the polarizer protecting film include acellulose-based film, an acrylic film, a polyester-based film, anorbornene-based film, and a cycloolefin-based film. The polarizerprotecting film may have undergone any of various surface treatments.Examples of various surface treatments include hard coating treatments,antireflection treatments, and treatments for any other purpose such asanti-sticking, diffusion or antiglare purposes. The release film isprovided on the optical member with the adhesive interposedtherebetween.

When no external force is applied, the sheet material curls in thelongitudinal direction so that the release film is facing inward. Whenthe main component of the sheet material is the optical member and whenthe other members (such as the release film) are considered to havesubstantially no effect, factors for the curling properties are derivedfrom the optical member.

Hereinafter, the direction of the feeding and transporting of the sheetmaterial from the roll (feed direction) is also referred to as MD, andthe direction perpendicular to the feed direction is also referred to asTD.

The sheet material is fed from the roll and cut by cutting means, whilethe release film is left uncut (cutting step). In this step, whileleaving the release film uncut, the other members of the sheet materialare cut into a piece or pieces. For example, when the sheet material isa laminate of a surface protecting member, an optical member, anadhesive, and a release film, the members other than the release film,namely, the surface protecting member, the optical member and theadhesive are cut.

Thereafter, as shown in FIG. 19, the cut piece composed of the membersof the sheet material other than the release film may be turned backalong the feeding line. Even in such a case, the sheet material curlswith the release film facing inward, so that the other members areprevented from peeling from the cut portion.

After the cutting step, the cut piece of the sheet material is bonded tothe substrate with the adhesive interposed therebetween, while therelease film is removed (bonding step). Since the sheet material isbonded to the substrate while peeling off the release film, the opticalmember as a component of the sheet material can be bonded to thesubstrate while inhibiting the sheet material from curling. Examples ofthe substrate include a liquid crystal cell glass substrate, an organicEL emitting material substrate, and so on. In a preferred mode, thesubstrate is previously subjected to a cleaning treatment before thebonding.

According to the feature of the invention, the sheet material has thecurling properties, and therefore, even when the other members of thesheet material are cut with the release film left uncut, the cut membersare prevented from peeling from the release film during the subsequentfeeding, so that the cut members can be bonded to the substrate withhigh accuracy.

The method for manufacturing the optical display unit, which includesbonding a sheet material (hereinafter also referred to as a first sheetmaterial) to one side of the substrate, may also include bonding a sheetmaterial (hereinafter also referred to as a second sheet material) tothe other side in the same manner.

In an embodiment of the invention, a cut sample of the sheet materialmay have a curling amount of 5 mm to 100 mm, when it is placed on a flatsurface so that it can curl to become convex downwardly, wherein thesample is obtained by cutting the sheet material in a length of 29.7 cmparallel to the longitudinal direction and in a width of 21.0 cmperpendicular to the longitudinal direction, and the curling amount isthe height of an edge of the sample from the flat surface. In view ofbonding accuracy, the curling amount is preferably 80 mm or less. Inorder to prevent peeling more reliably, the curling amount is morepreferably 10 mm or more. This feature is effective and advantageous asdescribed above.

In an embodiment of the invention, the sheet material may be wound intoa roll so that the release film of the sheet material can be placedinside. This feature is also effective and advantageous as describedabove.

In an embodiment of the invention, the optical member may include afirst film provided on one side of the polarizer, a second film providedon the other side of the polarizer, and an adhesive provided on thesecond film, wherein

the release film is provided on the second film with the adhesiveinterposed therebetween, and

the longitudinal dimensional change rate of the first film is lower thanthe longitudinal dimensional change rate of the second film. Thisfeature is effective and advantageous as described above.

In an embodiment of the invention, the method for manufacturing anoptical display unit may further include:

a release film removing step including feeding the sheet material fromthe roll and removing the release film;

a defect inspecting step including performing defect inspection afterthe release film removing step; and

a release film bonding step including bonding a release film to thesheet material with the adhesive interposed therebetween, after thedefect inspecting step, wherein

in the cutting step, the sheet material is cut into a predetermined sizewithout cutting the newly bonded release film. The defect inspection canbe performed on the sheet material without the need to take into accountthe inherent retardation of the release film and defects in the releasefilm, such as foreign matter or scratches deposited on or present in therelease film. The release film to be newly bonded may be a new one or aused one. When the release film is a used one, it is preferably checkedin advance to be sure that it does not have any problem such as foreignmatter, stain, or breakage, before use.

The sheet material also has curling properties. For example, the curlingproperties may be caused by a difference between the components of theoptical member (e.g., a difference in thickness, type, dimensionalchange rate, or the like), by the conditions of the manufacture of theoptical film, or by the adhesive used to bond the members together. Thetendency to curl along the longitudinal direction may be enhanced bywinding the continuous sheet material into a roll.

Another embodiment of the invention is directed to a method formanufacturing an optical display unit including a substrate and anoptical member that includes a polarizer and is bonded to the substratewith an adhesive interposed therebetween, which includes:

a carrier film bonding step including feeding a continuous sheetmaterial from a roll of the continuous sheet material, wherein thecontinuous sheet material includes the optical member and a release filmprovided on one side of the optical member with the adhesive interposedtherebetween, and bonding a carrier film to an opposite side of thesheet material from the release film side;

a cutting step including cutting the sheet material by cutting means,while leaving the carrier film uncut; and

a bonding step including peeling off the release film from the sheetmaterial by peeling means and bonding the sheet material to thesubstrate with the adhesive interposed therebetween, while peeling offthe carrier film, wherein

when no external force is applied, the sheet material curls in thelongitudinal direction so that the release film is facing outward.

This feature is effective and advantageous as described below. Thecontinuous sheet material is provided in the form of a roll. The sheetmaterial includes at least an optical member and a release film andtypically further includes a peelable surface protecting member providedon the surface of the optical member. The optical member may include atleast a polarizer and a polarizer protecting film. When the maincomponent of the sheet material is the optical member and when the othermembers (such as the release film) are considered to have substantiallyno effect, factors for the curling properties are derived from theoptical member. The release film is provided on the optical member withthe adhesive interposed therebetween. When no external force is applied,the sheet material curls in the longitudinal direction so that therelease film is facing outward. For example, the continuous sheetmaterial may be wound into a roll so that the release film can be placedoutside. The method for measuring the curling is as described above.

Subsequently, the sheet material is fed from the roll, and the carrierfilm is bonded to the opposite side of the sheet material from therelease film side with the adhesive interposed therebetween (carrierfilm bonding step). The sheet material is then cut using cutting means,while the carrier film and the adhesive are left uncut (cutting step).Thus, the sheet material is cut with the carrier film and the adhesiveleft uncut.

After the cutting step, the release film is peeled off from the sheetmaterial by peeling means, and the sheet material is bonded to thesubstrate with the adhesive interposed therebetween, while the carrierfilm and the adhesive are peeled off (bonding step). Since the sheetmaterial is bonded to the substrate while peeling off the carrier filmand the adhesive, the optical member as a component of the sheetmaterial can be bonded to the substrate while inhibiting the sheetmaterial from curling.

The sheet material curls so that the release film is facing outward, andtherefore, it curls so that the carrier film is facing inward. Thus,when the sheet material is cut with the carrier film left uncut, peelingof the sheet material from the carrier film is well suppressed duringfeeding. For example, on a roller R as shown in FIG. 19, therefore,peeling of the cut piece of the sheet material from the carrier film canbe well suppressed, so that the cut piece can be bonded to the substratewith high accuracy. According to the feature of the invention, the sheetmaterial has the curling properties, and therefore, even when the sheetmaterial is cut with the carrier film left uncut, the cut piece of thesheet material is prevented from peeling from the carrier film duringthe subsequent feeding, so that the sheet material can be bonded to thesubstrate with high accuracy.

In an embodiment of the invention, the amount of curling in thelongitudinal direction in such a manner that the release film is facingoutward is preferably from 5 mm to 100 mm. This means that the materialcurls in the plus curling direction.

A further embodiment of the invention is also directed to a method formanufacturing an optical display unit including a substrate and anoptical member that includes a polarizer and is bonded to the substratewith an adhesive interposed therebetween, which includes:

a cutting step including feeding a continuous sheet material from a rollof the continuous sheet material, wherein the continuous sheet materialincludes the optical member, a release film provided on one side of theoptical member with the adhesive interposed therebetween, and a surfaceprotecting member provided on the opposite side of the optical memberfrom the release film side, and cutting the sheet material by cuttingmeans, while leaving the surface protecting member uncut;

a bonding step including peeling off the release film from the sheetmaterial by peeling means and bonding the sheet material to thesubstrate with the adhesive interposed therebetween; and

a cutting step including cutting the surface protecting member, wherein

when no external force is applied, the sheet material curls in thelongitudinal direction so that the release film is facing outward.

This feature is effective and advantageous as described below. First,the continuous sheet material is provided in the form of a roll. Thesheet material includes at least an optical member, a release film and asurface protecting member provided on the opposite side from the releasefilm side. The surface protecting member may be provided with or withoutan adhesive. The optical member may include at least a polarizer and apolarizer protecting film. When no external force is applied, the sheetmaterial curls in the longitudinal direction so that the release film isfacing outward. When no external force is applied, therefore, the sheetmaterial curls so that the surface protecting member is facing inward.When the main component of the sheet material is the optical member andwhen the other members are considered to have substantially no effect,factors for the curling properties are derived from the optical member.The release film is provided on the optical member with the adhesiveinterposed therebetween. For example, the continuous sheet material maybe wound into a roll so that the release film can be placed outside.

The first sheet material is fed from the roll, and while the surfaceprotecting member is left uncut, the other members of the sheet materialare cut by cutting means (cutting step). When the surface protectingmember is provided on the optical member with an adhesive interposedtherebetween, the members other than the surface protecting member andthe adhesive may be cut. In this cutting step, the cut piece composed ofthe other members of the sheet material is formed on the surfaceprotecting member, so that curling of the optical member or the whole ofthe sheet material can be suppressed.

After the cutting step, the release film is peeled off from the sheetmaterial by peeling means. The cut piece composed of the other member ofthe sheet material is then bonded to the substrate with the adhesiveinterposed therebetween (bonding step). Subsequently, the surfaceprotecting member is cut (cutting step).

The sheet material curls so that the release film is facing outward, andtherefore, it curls so that the surface protecting member is facinginward. Thus, when the sheet material is cut with the surface protectingmember left uncut, peeling of the other members of the sheet materialfrom the surface protecting member is well suppressed. For example, on aroller R as shown in FIG. 19, therefore, peeling of the cut piece(composed of the other members of the sheet material) from the surfaceprotecting film can be well suppressed, so that the cut piece can bebonded to the substrate with high accuracy. According to the feature ofthe invention, the sheet material has the curling properties, andtherefore, even when the sheet material is cut with the surfaceprotecting member left uncut, the cut piece composed of the othermembers of the sheet material is prevented from peeling from the surfaceprotecting member during the subsequent feeding, so that the sheetmaterial can be bonded to the substrate with high accuracy.

In an embodiment of the invention, the amount of curling in thelongitudinal direction in such a manner that the release film is facingoutward is preferably from 5 mm to 100 mm. This means that the materialcurls in the plus curling direction.

In an embodiment of the invention, the optical display unit preferablyhas a diagonal size in the range of 14 to 120 inches. This is becausethe larger the size, the more the optical member curls. The invention isalso effective for an optical member with high curling properties, eventhough the optical member has a size of less than 14 inches. Opticaldisplay units generally used have a size of 82 inches or less.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow chart of the method of Embodiment 1 for manufacturingan optical display unit;

FIG. 2 is a schematic diagram for illustrating an optical member inEmbodiment 1;

FIG. 3 is a schematic diagram for illustrating an optical film inanother mode of Embodiment 1;

FIG. 4 is a schematic diagram for illustrating an optical member inEmbodiment 2;

FIG. 5 is a schematic diagram for illustrating an optical film inanother mode of Embodiment 2;

FIG. 6 is a flow chart of the method of Embodiment 3 for manufacturingan optical display unit;

FIG. 7 is a schematic diagram for illustrating an optical member inEmbodiment 3;

FIG. 8 is a schematic diagram for illustrating an optical film inanother mode of Embodiment 3;

FIG. 9 is a schematic diagram for illustrating an optical member inEmbodiment 4;

FIG. 10 is a schematic diagram for illustrating an optical member inanother mode of Embodiment 4;

FIG. 11A is a diagram for illustrating the configuration of amanufacturing system according to the invention;

FIG. 11B is a diagram for illustrating the configuration of amanufacturing system according to the invention;

FIG. 12 is a diagram for illustrating a method for measuring elasticmoduli;

FIG. 13 is a diagram for illustrating a method for measuring the amountof curling;

FIG. 14 is a diagram for illustrating a method for measuring the amountof curling;

FIG. 15 is a diagram for illustrating a cutting method and a bondingmethod in another embodiment;

FIG. 16 is a diagram for illustrating a cutting method and a bondingmethod in a further embodiment;

FIG. 17 is a diagram for illustrating a method for measuring the bondingaccuracy in the examples;

FIG. 18 is a flow chart of a conventional method for manufacturing anoptical display unit; and

FIG. 19 is a diagram for illustrating peeling of a sheet material duringfeeding.

DESCRIPTION OF REFERENCE CHARACTERS

In the drawings, reference character 1 represents a first sheetmaterial, 2 a second sheet material, 11 a first optical member, 11 a apolarizer, 11 b a first film, 12 a first release film, 13 a protectivefilm, 14 a first adhesive, 21 a second optical member, 21 a a polarizer,21 b a second film, 22 a second release film, 23 a protective film, 24 asecond adhesive, and A a substrate.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

Embodiment 1 of the invention is described below. FIG. 1 shows a flowchart of the method of Embodiment 1 for manufacturing an optical displayunit. FIG. 2 shows a schematic diagram of the structure of first andsecond optical members for use in Embodiment 1 and the structure of alaminate of the optical members and a substrate. In Embodiments 1 to 4described below, first and second sheet materials each curl so that therelease film is facing inward.

(1) Step of Providing First Material Roll (S1 in FIG. 1). A first rollof a first continuous sheet material is provided. As shown in FIG. 2,the laminated structure of the first sheet material 1 includes a firstoptical member 11, a first release film 12 and a surface protecting film13. The first optical member 11 includes a first polarizer 11 a and afirst film 11 b provided on one side thereof with a bonding adhesivelayer (not shown) interposed therebetween. The feed-direction elasticmodulus of the first polarizer 11 a differs from that of the first film11 b. The first sheet material 1 curls in the longitudinal direction sothat the first release film 12 is facing inward. The first film 11 b isa polarizer protecting film (e.g., a triacetylcellulose film). The firstfilm 11 b may have undergone a surface treatment. The elastic modulus inthe feed direction (feed-direction elastic modulus) can be changed bythe surface treatment. Examples of the surface treatment include a hardcoating treatment, an antireflection treatment, and a treatment for anyother purpose such as anti-sticking, diffusion or antiglare purpose. Thefirst release film 12 is provided on the first polarizer 11 a with afirst adhesive 14 interposed therebetween. The surface protecting film13 is provided on the first film 11 b with an adhesive 15 interposedtherebetween.

A method for measuring the “elastic modulus” is described below. The“elastic modulus” corresponds to tensile elastic modulus. A sample striphaving a width of 10 mm and a sufficient length in the measurementdirection is obtained by cutting and subjected to a measurement with atension tester (Tensilon) under a temperature environment at 25° C. andthe conditions described below. The tensile elastic modulus isdetermined from the resulting S-S (Strain-Strength) curve. When thefeed-direction elastic modulus (also referred to as “MD elasticmodulus”) is measured, the sample strip obtained by cutting is 10 mmwide in the direction perpendicular to the feed direction and, forexample, 100 mm long in the feed direction. When the elastic modulus inthe direction perpendicular to the feed direction (also referred to as“TD elastic modulus”) is measured, the sample strip obtained by cuttingis 10 mm wide in the feed direction and, for example, 100 mm long in thedirection perpendicular to the feed direction.

The measurement is performed under the conditions of a tension speed of50 mm/minute, a chuck-chuck distance of 10 mm, and room temperature. Theelastic modulus is determined from the S-S curve by the method describedbelow. As shown in FIG. 12, a tangent line is dawn from the initial risepoint of the S-S curve, and the strength is read at the point where anextension of the tangent line reaches 100% strain. The read value isdivided by the cross-sectional area of the sample strip(thickness×sample width (10 mm)), and the quotient is used as thetensile elastic modulus (also generally called Young's modulus).

Table 1 shows examples of the measurement of the elastic modulus anddimensional change rate of polarizers and various films, which are usedto form the first optical member and the second optical member describedbelow.

TABLE 1 Dimensional change Thickness rate (%, 70° C.) Elastic modulus(MPa) (μm) MD TD MD TD Remarks Stretched PVA 30 0.1 — 20,000 — *1(polarizer) TAC1 40 0.2 0.1 2,500 2,000 KC4UY manufactured by KonicaMinolta TAC2 80 0.1 0.2 1,500 2,000 TD-80UL manufactured by FujifilmCorporation TAC3 40 0.8 0.8 1,800 1,800 KC-4FR manufactured by KonicaMinolta TAC4 80 — — 2,000 2,000 WVBZ Film manufactured by FujifilmCorporation Norbornene-based 1 70 0.4 0.4 1,200 1,200 Zeonor Film Δnd =65 nm (Zeonor) manufactured by ZEON CORPORATION Norbornene-based 2 50 11 1,000 1,000 Arton (note 1) (Arton) manufactured by JSR CorporationPolycarbonate — — — 2,400 — PP Non-stretched 50 — — 700 700 Biaxially-20 — — 1,900 3,400 stretched Acrylic 1 30 0.6 0.6 1,500 1,500 The resinof Example 1 disclosed in JP-A No. 2000-230016 PET 38 0.01 0.01 3,4003,900 T100 (38 μm) manufactured by Mitsubishi Polyester Film Inc. *1: Apolyvinyl alcohol film (99.5% in saponification degree, 2,400 inpolymerization degree, 75 μm in thickness, manufactured by KURARAY CO.,LTD.) was immersed in the baths under the conditions below for thepreparation. (A) The film was allowed to swell in a water bath at 30° C.(B) The film was dyed in an aqueous iodine solution at 30° C. (C) Thefilm was crosslinked in an aqueous boric acid solution at 30° C. (D) Thefilm was stretched to 5 times the initial length of the raw film in awaterbath at 60° C. (E) The color tone of the film was controlled in anaqueous KI solution at 30° C. (Note 1) Arton is a product obtained bystretching an Arton film to 1.5 times in the film-feed direction at atemperature of 155° C. or less.

As is evident from the measurement examples in Table 1, polarizers andvarious films have different elastic moduli and different dimensionalchange rates, which impart curling properties to the optical member as awhole. When allowed to run along the feeding line, the optical member inthe form of a continuous sheet material is inhibited from curling.During the feeding, however, the problem of peeling of the half-cutmember occurs during the feeding, depending on the curling direction orthe degree of curling. In the embodiments, the problem of peeling issolved by the feature that the sheet material curls in the longitudinaldirection so that the release film is facing inward.

(2) First Cutting Step (S2 in FIG. 1). Subsequently, the first sheetmaterial is fed from the first roll provided and placed, and the firstsheet material is cut using cutting means, while the first release film12 is left uncut. Thus, the members of the sheet material other than thefirst release film 12, namely, the surface protecting film 13, theadhesive 15, the first optical member 11, and the first adhesive 14 arecut. For example, the cutting means is a laser, a cutter, or any otherknown cutting device.

(3) First Bonding Step (S3 in FIG. 1). After the first cutting step, thecut piece composed of the other members of the first sheet material 1 isbonded to a substrate A with the first adhesive 14 interposedtherebetween, while the first release film 12 is removed. Therefore,even when the first release film 12 is peeled off, the first sheetmaterial 1 can be inhibited from curling in the process of bonding thefirst optical member 11 to the substrate A. For example, the substrate Ais a liquid crystal cell substrate, an organic EL emitting materialsubstrate, or the like. The substrate A is previously subjected to acleaning treatment before the bonding.

The steps of providing the first material roll, first cutting, and firstbonding are each performed in a continuous manufacturing line. A seriesof the above manufacturing steps are to bond the first optical member 11to one side of the substrate A. The manufacturing steps to bond a secondoptical member 21 to the other side are described below.

(4) Step of Providing Second Material Roll (S4 in FIG. 1). A second rollof a second continuous sheet material 2 is provided. As shown in FIG. 2,the laminated structure of the second sheet material 2 includes a secondoptical member 21, a second release film 22 and a surface protectingfilm 23. The second optical member 21 includes a second polarizer 21 aand a second film 21 b provided on one side thereof with an adhesivelayer (not shown) interposed therebetween. The feed-direction elasticmodulus of the second polarizer 21 a differs from that of the secondfilm 21 b. The second film 21 b is a polarizer protecting film (e.g., atriacetylcellulose film). The second release film 22 is provided on thesecond polarizer 21 a with a second adhesive 24 interposed therebetween.The surface protecting film 23 is provided on the second film 21 b withan adhesive 25 interposed therebetween.

(5) Second Cutting Step (S5 in FIG. 1). Subsequently, the second sheetmaterial 2 is fed from the second roll provided and placed, and whilethe second release film 22 is left uncut, the other members of thesecond sheet material 2 are cut using cutting means. Thus, the surfaceprotecting film 23, the adhesive 25, the second optical member 21, andthe second adhesive 24 are cut, while the second release film 22 is leftuncut. For example, the cutting means is a laser, a cutter, or any otherknown cutting device.

(6) Second Bonding Step (S6 in FIG. 1). After the second cutting step,the cut piece composed of the other members of the second sheet materialis bonded to the other side of the substrate A, which is opposite fromthe side where the first optical member 11 is bonded, with the secondadhesive 24 interposed therebetween, while the second release film 22 isremoved. Therefore, even when the second release film 22 is peeled off,the second sheet material can be inhibited from curling in the processof bonding the second optical member 21 to the substrate A. As a result,an optical display unit is manufactured that includes the substrate Aand optical members provided on both sides, which include the firstoptical member 11 bonded to one side thereof and the second opticalmember 21 bonded to the other side thereof.

The steps of providing the first material roll, first cutting, firstbonding, providing the second material roll, second cutting, and secondbonding are each performed in a continuous manufacturing line.

(7) Preferably, the continuous process further includes an inspectingstep (S7 in FIG. 1). Examples of the inspecting step include the step ofinspecting the bonded state and the step of inspecting any defect afterthe bonding. Both inspections are preferably performed, while any one ofthe inspections may be performed.

(8) The substrate determined as non-defective in the inspecting step isimplemented into an optical display device (implementing step). When itis determined as defective, it is subjected to a reworking process inwhich a new sheet material (or a new optical film) is bonded and theninspected, and when the product is determined as non-defective, it issubjected to the implementing step, but when the product is determinedas defective, it is subjected to the reworking process again ordiscarded. The surface protecting film may be peeled off from theoptical member as needed in each manufacturing step.

Another Mode of Embodiment 1

Another mode of Embodiment 1 is described below. In this mode, themanufacturing steps are the same as the manufacturing steps (1) to (8)described above, and a description thereof will be omitted. FIG. 3 showsa schematic diagram of the structure of another version of the secondsheet material.

As shown in FIG. 3, the laminated structure of the second sheet material2 includes a second optical member 21, a second release film 22 and asurface protecting film 23. The second optical member 21 includes asecond polarizer 21 a, a second film 21 b provided on one side thereofwith a bonding adhesive layer (not shown) interposed therebetween, athird film 21 c provided on the other side of the second polarizer 21 awith a bonding adhesive layer (not shown) interposed therebetween, and afourth film 21 d provided on the third film 21 c with a bonding adhesivelayer (not shown) interposed therebetween. The second sheet material 2curls in the longitudinal direction so that the second release film 22is facing inward. The second film 21 b and the third film 21 c are eacha polarizer protecting film (e.g., a triacetylcellulose film). Thefourth film 21 d is a retardation film (e.g., a PI film). The second andthird films 21 b and 21 c, which are opposed to each other with thepolarizer 21 a interposed therebetween, have different feed-directionelastic moduli. The feed-direction elastic modulus of the fourth film 21d may also differ from those elastic moduli. The second release film 22is provided on the fourth film 21 d with a second adhesive 24 interposedtherebetween. The surface protecting film 23 is provided on the secondfilm 21 b with an adhesive 25 interposed therebetween.

Embodiment 2

Embodiment 2 of the invention is described below. In this embodiment,the manufacturing steps are the same as the manufacturing steps (1) to(8) described above for Embodiment 1, and a description thereof will beomitted. FIG. 4 shows a schematic diagram of the structure of first andsecond optical members for use in Embodiment 2.

FIG. 4 shows an example of the laminated structure of a first sheetmaterial 1. The first sheet material 1 includes a first optical member111, a first release film 12 and a surface protecting film 13. The firstoptical member 111 includes a first polarizer 111 a, a first film 111 bprovided on one side thereof with a bonding adhesive layer (not shown)interposed therebetween, and a second film 111 c provided on the otherside of the first polarizer 111 a with a bonding adhesive layer (notshown) interposed therebetween. The first and second films 111 b and 111c, which are opposed to each other with the first polarizer 111 ainterposed therebetween, have different feed-direction elastic moduli.The first sheet material 1 curls in the longitudinal direction so thatthe first release film 12 is facing inward. The first film 111 b mayhave undergone a surface treatment. The feed-direction elastic modulusis also changed by the surface treatment. The first release film 12 isprovided on the second film 111 c with a first adhesive 14 interposedtherebetween. The surface protecting film 13 is provided on the firstfilm 111 b with an adhesive 15 interposed therebetween. The first andsecond films 111 b and 111 c are each a polarizer protecting film.

Examples of a combination of the first and second films 111 b and 111 cinclude a combination of a TAC film and a TAC film, a combination of aTAC film and an Arton film, a combination of a TAC film and a Zeonorfilm, and a combination of a TAC film and a polypropylene film. Forexample, the TAC film is selected from KC4UY manufactured by KonicaMinolta, KC-4FR manufactured by Konica Minolta, TD-80UL manufactured byFujifilm Corporation, WVBZ Film manufactured by Fujifilm Corporation,and so on.

As shown in FIG. 4, the laminated structure of a second sheet material 2includes a second optical member 121, a second release film 22 and asurface protecting film 23. The second optical member 121 includes asecond polarizer 121 a and a third film 121 b provided thereon with abonding adhesive layer (not shown) interposed therebetween. Thefeed-direction elastic modulus of the second polarizer 121 a differsfrom that of the third film 121 b. The second sheet material curls inthe longitudinal direction so that the second release film 22 is facinginward. The third film 121 b is a polarizer protecting film (e.g., a TACfilm). The second release film 22 is provided on the second polarizer121 a with a second adhesive 24 interposed therebetween. The surfaceprotecting film 23 is provided on the third film 121 b with an adhesive25 interposed therebetween.

Another Mode of Embodiment 2

Another mode of Embodiment 2 is described below. In this embodiment, asecond optical member 121 with a different structure is used instead.FIG. 5 shows a schematic diagram of the structure of another version ofthe second sheet material 2.

As shown in FIG. 5, the laminated structure of the second sheet material2 includes a second optical member 221, a second release film 22 and asurface protecting film 23. The second optical member 221 includes asecond polarizer 221 a, a third film 221 b provided on one side thereofwith a bonding adhesive layer (not shown) interposed therebetween, and afourth film 221 c provided on the other side of the second polarizer 221a with a bonding adhesive layer (not shown) interposed therebetween. Thethird and fourth films 221 b and 221 c, which are opposed to each otherwith the second polarizer 221 a interposed therebetween, have differentfeed-direction elastic moduli. The second sheet material curls in thelongitudinal direction so that the second release film 22 is facinginward. The second release film 22 is provided on the fourth film 221 cwith a second adhesive 24 interposed therebetween. The surfaceprotecting film 23 is provided on the third film 221 b with an adhesive25 interposed therebetween. The third and fourth films 221 b and 221 care each a polarizer protecting film.

Examples of a combination of the third and fourth films 221 b and 221 cinclude a combination of a TAC film and a TAC film, a combination of aTAC film and an Arton film, a combination of a TAC film and a Zeonorfilm, a combination of a TAC film and a polypropylene film, acombination of an acrylic film and a KC-4FR film manufactured by KonicaMinolta, a combination of an acrylic film and a WVBZ film, a combinationof an acrylic film and an Arton film, a combination of an acrylic filmand a Zeonor film, a combination of an acrylic film and a polypropylenefilm, a combination of a polyethylene terephthalate film and a KC-4FRfilm manufactured by Konica Minolta, a combination of a polyethyleneterephthalate film and a WVBZ film, a combination of a polyethyleneterephthalate film and an Arton film, a combination of a polyethyleneterephthalate film and a Zeonor film, and a combination of apolyethylene terephthalate film and a polypropylene film. For example,the TAC film is selected from KC4UY manufactured by Konica Minolta,KC-4FR manufactured by Konica Minolta, TD-80UL manufactured by FujifilmCorporation, WVBZ Film manufactured by Fujifilm Corporation, and so on.

Examples of a combination (of the first and second films 111 b and 111c) in the first optical member 111 versus a combination (of the thirdand fourth films 221 b and 221 c) in the second optical member 221include a combination of a TAC film and a TAC film versus a combinationof a TAC film and a WVBZ film, a combination of a TAC film and an Artonfilm, a combination of a TAC film and a Zeonor film, a combination of anacrylic film and a WVBZ film, a combination of an acrylic film and anArton film, a combination of an acrylic film and a Zeonor film, acombination of a polyethylene terephthalate film and a WVBZ film, acombination of a polyethylene terephthalate film and an Arton film, or acombination of a polyethylene terephthalate film and a Zeonor film; acombination of a TAC film and a KC-4FR film versus a combination of aTAC film and a KC-4FR film, a combination of an acrylic film and aKC-4FR film or a combination of a polyethylene terephthalate film and aKC-4FR film; a combination of a TAC film and an Arton film versus acombination of a TAC film and an Arton film, a combination of a TAC filmand a Zeonor film, a combination of an acrylic film and an Arton film, acombination of an acrylic film and a Zeonor film, a combination of apolyethylene terephthalate film and an Arton film, or a combination of apolyethylene terephthalate film and a Zeonor film; a combination of aTAC film and a Zeonor film versus a combination of a TAC film and anArton film, a combination of a TAC film and a Zeonor film, a combinationof an acrylic film and an Arton film, a combination of an acrylic filmand a Zeonor film, a combination of a polyethylene terephthalate filmand an Arton film, or a combination of a polyethylene terephthalate filmand a Zeonor film; and a combination of a TAC film and a polypropylenefilm versus a combination of a TAC film and a polypropylene film, acombination of an acrylic film and a polypropylene film, or acombination of a polyethylene terephthalate film and a polypropylenefilm.

Skip Cutting Method

Another mode of the first and second cutting steps is described below.Information about defects in each of the first and second sheetmaterials (such as coordinates of defects, defect type, and defect size)may be attached as coded information (such as QR codes or bar codes) toone widthwise end portion of each of the first and second materialrolls. In such a case, the coded information may be read and analyzed ata stage before cutting, and then in each of the first and second cuttingsteps, the material may be cut into a specific size so that the defectscan be separated (this process is also referred to as skip cutting). Thesystem may be configured so that the defect-containing portion can berejected or bonded to a certain member other than the substrate and thatthe cut piece of the optical member having a specific size anddetermined as non-defective can be bonded to the substrate. This processsignificantly improves the yields of the optical display unit.

Embodiment 3

Embodiment 3 of the invention is described below. FIG. 6 shows a flowchart of the method of Embodiment 3 for manufacturing an optical displayunit. FIG. 7 shows a schematic diagram of the structure of first andsecond optical members for use in Embodiment 3.

(1) Step of Providing First Material Roll (S1 in FIG. 6). A first rollof a first continuous sheet material is provided. As shown in FIG. 7,the laminated structure of the first sheet material 1 includes a firstoptical member 11, a first release film 12 and a surface protecting film13. The first optical member 11 includes a first polarizer 11 a and afirst film 11 b provided on one side thereof with a bonding adhesivelayer (not shown) interposed therebetween. The feed-direction elasticmodulus of the first polarizer 11 a differs from that of the first film11 b. The first sheet material 1 curls in the longitudinal direction sothat the first release film 12 is facing inward. The first film 11 b isa polarizer protecting film (e.g., a triacetylcellulose film). The firstfilm 11 b may have undergone a surface treatment. The first release film12 is provided on the first polarizer 11 a with a first adhesive 14interposed therebetween. The surface protecting film 13 is provided onthe first film 11 b with an adhesive 15 interposed therebetween.

(2) Step of Removing first Release Film (S61 in FIG. 6). The first sheetmaterial 1 is then fed from the first roll provided and placed, and thefirst release film 12 is removed. Examples of a method for removing thefirst release film 12 include a method including continuouslydelaminating the film, while winding the delaminated film into a roll, amethod including cutting only the first release film into a unit of agiven size and delaminating and removing the unit with an adhesive tape,and other known removing methods.

(3) First Defect Inspecting Step (S62 in FIG. 6). After the step ofremoving the first release film, defect inspection is performed. Defectinspection can be performed on the first optical member 11 without theneed to take into account the inherent retardation of the first releasefilm 12. Defect inspection may be performed using known methods.

(4) Step of Bonding Second Release Film (S63 in FIG. 6). After the firstdefect inspecting step, a second release film 12 a is bonded to thefirst polarizer 11 a with the first adhesive 14 interposed therebetween.In order to maintain the flatness, the bonding step is preferablyperformed so that bubbles such as air bubbles can be prevented frombeing trapped.

(5) First Cutting Step (S64 in FIG. 6). After the step of bonding thesecond release film, the other members of the first sheet material arecut using cutting means, while the second release film 12 a is leftuncut. Therefore, the surface protecting film 13, the adhesive 15, thefirst optical member 11, and the first adhesive 14 may be cut, while thesecond release film 12 a is left uncut.

(6) First Bonding Step (S65 in FIG. 6). After the first cutting step,the cut piece composed of the other members of the first sheet materialis bonded to a substrate A with the first adhesive 14 interposedtherebetween, while the second release film 12 a is removed. Therefore,even when the second release film 12 a is peeled off, the first sheetmaterial 1 can be inhibited from curling in the process of bonding thefirst optical member 11 to the substrate A.

The steps of providing the first material roll, removing the firstrelease film, first defect inspection, bonding the second release film,first cutting, and first bonding are each performed in a continuousmanufacturing line. A series of the above manufacturing steps are tobond the first optical member 11 to one side of the substrate A. Themanufacturing steps to bond a second optical member 21 to the other sideare described below.

(7) Step of Providing Second Material Roll (S4 in FIG. 6). A second rollof a second continuous sheet material 2 is provided. As shown in FIG. 7,the laminated structure of the second sheet material 2 includes a secondoptical member 21, a third release film 22 and a surface protecting film23. The second optical member 21 includes a second polarizer 21 a and asecond film 21 b provided on one side thereof with an adhesive layer(not shown) interposed therebetween. The feed-direction elastic modulusof the second polarizer 21 a differs from that of the second film 21 b.The second sheet material 2 curls in the longitudinal direction so thatthe third release film 22 is facing inward. The second film 21 b is apolarizer protecting film (e.g., a triacetylcellulose film). The thirdrelease film 22 is provided on the second polarizer 21 a with a secondadhesive 24 interposed therebetween. The surface protecting film 23 isprovided on the second film 21 b with an adhesive 25 interposedtherebetween.

(8) Step of Removing Third Release Film (S66 in FIG. 6). The secondsheet material is then fed from the second roll provided and placed, andthe third release film 22 is removed. The method described above or thelike may be used to remove the third release film 22.

(9) Second Defect Inspecting Step (S67 in FIG. 6). After the step ofremoving the third release film, defect inspection is performed. Defectinspection can be performed on the second optical member 21 without theneed to take into account the inherent retardation of the third releasefilm 22. Defect inspection may be performed using known methods.

(10) Step of Bonding Fourth Release Film (S68 in FIG. 6). After thesecond defect inspecting step, a fourth release film 22 a is bonded tothe second polarizer 21 a with the second adhesive 24 interposedtherebetween. In order to maintain the flatness, the bonding step ispreferably performed so that bubbles such as air bubbles can beprevented from being trapped.

(11) Second Cutting Step (S69 in FIG. 6). After the step of bonding thefourth release film, the other members of the second sheet material 2are cut using cutting means, while the fourth release film 22 a is leftuncut. Therefore, the surface protecting film 23, the adhesive 25, thesecond optical member 21, and the second adhesive 24 may be cut, whilethe fourth release film 22 a is left uncut.

(12) Second Bonding Step (S70 in FIG. 6). After the second cutting step,the cut piece composed of the other members of the second sheet materialis bonded to the other side of the substrate A, which is opposite fromthe side where the first optical member 11 is bonded, with the secondadhesive 24 interposed therebetween, while the fourth release film 22 ais removed. Therefore, even when the fourth release film 22 a is peeledoff, the second optical member 21 can be inhibited from curling in theprocess of bonding the second optical member 21 to the substrate A. As aresult, an optical display unit is manufactured that includes thesubstrate A and optical members provided on both sides, which includethe first optical member 11 bonded to one side thereof and the secondoptical member 21 bonded to the other side thereof.

The steps of providing the first material roll, removing the firstrelease film, first defect inspection, bonding the second release film,first cutting, first bonding, providing the second material roll,removing the third release film, second defect inspection, bonding thefourth release film, second cutting, and second bonding are eachperformed in a continuous manufacturing line.

(13) Preferably, the continuous process further includes an inspectingstep (S7 in FIG. 6). The inspecting step, the implementing step, and thereworking process may be the same as those described above.

Another Mode of Embodiment 3

Another mode of Embodiment 3 is described below. In this mode, themanufacturing steps are the same as the manufacturing steps (1) to (13)described above, and a description thereof will be omitted. FIG. 8 showsa schematic diagram of the structure of another version of the secondsheet material 2.

As shown in FIG. 8, the laminated structure of the second sheet material2 includes a second optical member 21, a third release film 22 and asurface protecting film 23. The second optical member 21 includes asecond polarizer 21 a, a second film 21 b provided on one side thereofwith a bonding adhesive (not shown) interposed therebetween, a thirdfilm 21 c provided on the other side of the second polarizer 21 a with abonding adhesive layer (not shown) interposed therebetween, and a fourthfilm 21 d provided on the third film 21 c with a bonding adhesive layer(not shown) interposed therebetween. The second film 21 b and the thirdfilm 21 c are each a polarizer protecting film (e.g., atriacetylcellulose film). The fourth film 21 d is a retardation film(e.g., a PI film). The second and third films 21 b and 21 c, which areopposed to each other with the polarizer 21 a interposed therebetween,have different feed-direction elastic moduli. The feed-direction elasticmodulus of the fourth film 21 d may also differ from those elasticmoduli. The second sheet material 2 curls in the longitudinal directionso that the third release film 22 is facing inward. The third releasefilm 22 is provided on the fourth film 21 d with a second adhesive 24interposed therebetween. The surface protecting film 23 is provided onthe second film 21 b with an adhesive 25 interposed therebetween.

The third release film 22 is removed, before defect inspection isperformed. The fourth release film 22 a is then bonded to the third film21 d with the second adhesive 24 interposed therebetween. The cuttingstep and the second bonding step are then performed as described abovefor Embodiment 3.

Embodiment 4

Embodiment 4 of the invention is described below. In this embodiment,the manufacturing steps are the same as the manufacturing steps (1) to(14) described above for Embodiment 3, and a description thereof will beomitted. FIG. 9 shows a schematic diagram of the structure of first andsecond optical members for use in Embodiment 4.

FIG. 9 shows an example of the laminated structure of a first sheetmaterial 1. The first sheet material 1 includes a first optical member111, a first release film 12 and a surface protecting film 13. The firstoptical member 111 includes a first polarizer 111 a, a first film 111 bprovided on one side thereof with a bonding adhesive layer (not shown)interposed therebetween, and a second film 111 c provided on the otherside of the first polarizer 111 a with a bonding adhesive layer (notshown) interposed therebetween. The first and second films 111 b and 111c, which are opposed to each other with the first polarizer 111 ainterposed therebetween, have different feed-direction elastic moduli.The first sheet material curls in the longitudinal direction so that thefirst release film 12 is facing inward. The first film 111 b may haveundergone a surface treatment. The feed-direction elastic modulus isalso changed by the surface treatment. The first release film 12 isprovided on the second film 111 c with a first adhesive 14 interposedtherebetween. The surface protecting film 13 is provided on the firstfilm 111 b with an adhesive 15 interposed therebetween. The first film111 b is a polarizer protecting film.

Examples of a combination of the first and second films 111 b and 111 cinclude a combination of a TAC film and a TAC film, a combination of aTAC film and an Arton film, a combination of a TAC film and a Zeonorfilm, and a combination of a TAC film and a polypropylene film. Examplesof the structure of the TAC film include those described above.

As shown in FIG. 9, the first release film 12 is removed, and defectinspection is performed. A second release film 12 a is then bonded tothe second film 111 c with the first adhesive 14 interposedtherebetween.

As shown in FIG. 9, the laminated structure of a second sheet material 2includes a second optical member 121, a third release film 22 and asurface protecting film 23. The second optical member 121 includes asecond polarizer 121 a and a second film 121 b provided on one sidethereof with a bonding adhesive layer (not shown) interposedtherebetween. The feed-direction elastic modulus of the second polarizer121 a differs from that of the second film 121 b. The second sheetmaterial curls in the longitudinal direction so that the third releasefilm 22 is facing inward. The second film 121 b is a polarizerprotecting film (e.g., a TAC film). The third release film 22 isprovided on the second polarizer 121 a with a second adhesive 24interposed therebetween. The surface protecting film 23 is provided onthe second film 121 b with an adhesive 25 interposed therebetween.

As shown in FIG. 9, the second release film 22 is removed, and defectinspection is performed. A fourth release film 22 a is then bonded tothe second polarizer 121 a with the second adhesive 24 interposedtherebetween.

Another Mode of Embodiment 4

Another mode of Embodiment 4 is described below. In this embodiment, asecond optical member 221 with a different structure is used instead.FIG. 10 shows a schematic diagram of the structure of another version ofthe second sheet material 2.

As shown in FIG. 10, the laminated structure of the second sheetmaterial 2 includes a second optical member 221, a third release film 22and a surface protecting film 23. The second optical member 221 includesa second polarizer 221 a, a third film 221 b provided on one sidethereof with a bonding adhesive layer (not shown) interposedtherebetween, and a fourth film 221 c provided on the other side of thesecond polarizer 221 a with a bonding adhesive layer (not shown)interposed therebetween. The third and fourth films 221 b and 221 c,which are opposed to each other with the second polarizer 221 ainterposed therebetween, have different feed-direction elastic moduli.The second sheet material curls in the longitudinal direction so thatthe third release film 22 is facing inward. The third release film 22 isprovided on the fourth film 221 c with a second adhesive 24 interposedtherebetween. The surface protecting film 23 is provided on the thirdfilm 221 b with an adhesive 25 interposed therebetween.

As shown in FIG. 10, the third release film 22 is removed, and defectinspection is performed. A fourth release film 22 a is then bonded tothe fourth film 221 c with the second adhesive 24 interposedtherebetween. The third and fourth films 221 b and 221 c are each apolarizer protecting film.

Examples of a combination of the third and fourth films 221 b and 221 cinclude those listed above for a combination in another mode ofEmbodiment 2.

Examples of a combination (of the first and second films 111 b and 111c) in the first optical member 111 versus a combination (of the thirdand fourth films 221 b and 221 c) in the second optical member 221include those listed above for a combination versus a combination inanother mode of Embodiment 2.

Preferred Manufacturing Systems for Performing the Manufacturing Methodsof Embodiments 1 to 4

A preferred manufacturing system for performing the manufacturing methodof Embodiment 3 or 4 is described below. FIGS. 11A and 11B schematicallyshow the configuration of the manufacturing system.

As shown in FIGS. 11A and 11B, the manufacturing system includes: afirst manufacturing unit for bonding the first optical member 1 to thesubstrate and a second manufacturing unit for bonding the second opticalmember to the surface of the substrate other than the substrate surfaceto which the first optical member is bonded.

The first manufacturing unit includes: first mounting means on which thefirst roll of the first continuous sheet material 1 is mounted; firstfeeding means for feeding the first sheet material 1 from the firstmaterial roll; first release film-removing means for removing the firstrelease film from the first sheet material 1 being fed; first defectinspecting means for performing defect inspection after the removal ofthe first release film; second release film-bonding means for bondingthe second release film to the first sheet material 1 with the firstadhesive interposed therebetween after the first defect inspection;first cutting means for cutting the other members of the first sheetmaterial 1 with the second release film left uncut, after the bonding ofthe second release film; first bonding means for bonding the cut piececomposed of the other members of the first sheet material 1, from whichthe second release film is being removed, to the substrate with thefirst adhesive interposed therebetween after the first cutting; andfirst control means for synchronizing and controlling the respectivemeans.

The second manufacturing unit includes: second mounting means on whichthe second roll of the second continuous sheet material 2 is mounted;second feeding means for feeding the second sheet material from thesecond material roll; third release film-removing means for removing thethird release film from the second sheet material 2 being fed; seconddefect inspecting means for performing defect inspection after theremoval of the third release film; fourth release film-bonding means forbonding the fourth release film to the second sheet material 2 with theadhesive interposed therebetween after the second defect inspection;second cutting means for cutting the other members of the second sheetmaterial 2 with the fourth release film left uncut, after the bonding ofthe fourth release film; second bonding means for bonding the cut piececomposed of the other members of the second sheet material 2, from whichthe fourth release film is being removed, to the surface of thesubstrate other than the substrate surface to which the first opticalmember is bonded, with the second adhesive interposed therebetween; andsecond control means for synchronizing and controlling the respectivemeans.

The first and second manufacturing units may be each independentlydriven or driven in a synchronized manner. The first and second controlmeans may be used to drive and control a series of the steps in asynchronized manner. In the manufacturing methods of Embodiments 1 and2, the release film removing means, the defect inspecting means, and therelease film bonding means are omitted from the system.

First Manufacturing Unit

First mounting means 301 includes a roller mount apparatus on which thefirst roll of the first continuous sheet material 1 is mounted and whichis geared to a motor or the like to rotate freely or at a certain speed.The first control means controls the rotational speed and the driving.

First feeding means 302 feeds the first sheet material 1 from the firstroll and to each step. A tension controller is placed at a key point ineach step. The first feeding means 302 is controlled by the firstcontrol means 307.

The first release film-removing means is configured to delaminate andremove the first release film from the first sheet material 1 being fedand to wind it into a roll. The speed of winding it into the roll iscontrolled by the first control means. The delaminating mechanism (seeFIG. 11B) has a sharp-ended knife edge and is configured so that thefirst release film can be delaminated and removed by taking up the firstrelease film with the knife edge and turning the direction of thefeeding and that the first sheet material 1 separated from the firstrelease film can be fed in the feeding direction.

First defect inspecting means 303 inspects defects after the removal ofthe first release film. The first defect inspecting means 303 includes aCCD camera or a CMOS camera, and the image data taken by it are sent tothe first control means. The first control means analyzes the image datato detect defects and calculates their position coordinates. The defectposition coordinates are used in the skip cutting process with the firstcutting means described below.

Second release film-bonding means bonds the second release film to thefirst sheet material with the first adhesive interposed therebetweenafter the first defect inspection. As shown in FIG. 11A, the secondrelease film is unwound from a roll of the second release film, and thesecond release film and the first sheet material are inserted betweenone or more pairs of rollers so that they are bonded to each other undera certain pressure from the pair of rollers. The rotational speed of thepair of rollers, the pressure, and the feeding are controlled by thefirst control means.

While leaving the second release film uncut, first cutting means 304cuts the other members of the first sheet material 1 after the bondingof the second release film. The first cutting means 304 is a laser.Based on the defect position coordinates detected by the first defectinspection, the first cutting means 304 cuts the material into thepredetermined size in such a manner that defective portions can beseparated. Therefore, cut pieces having any defective portion arerejected as defective in a later step. Alternatively, the first cuttingmeans 304 may ignore defective portions and continuously cut thematerial into the predetermined size. In this case, the bonding processmay be designed not to bond, but to remove the defective portion or tobond the defective portion to a temporary plate unit, as describedbelow. In this case, the first control means also functions to controlthe process.

The first cutting means 304 also includes a holding table placed toadsorb and hold the first sheet material 1 from the back side, and thelaser is placed above the first sheet material 1. The laser is moved inthe horizontal direction to scan the first sheet material 1 in the widthdirection, so that the surface protecting film, the adhesive layer, thefirst optical member, and the first adhesive are cut at a predeterminedpitch in the feeding direction, while the second release film at thebottom is left uncut. In the laser system, an air nozzle for blowing awarm wind to the portion being cut and a smoke collecting duct forcollecting gas (smoke) generated from the portion being cut and carriedby the warm wind are preferably configured in combination and placedopposite to each other across the width of the first sheet material 1.The feeding mechanism includes step rollers 302 a and 302 b providedvertically movable upward and downward so that continuous feeding of thefirst sheet material 1 can be prevented from being stopped on theupstream and downstream sides when the holding table adsorbs the firstsheet material 1. This operation is also controlled by the first controlmeans.

After the first cutting process, first bonding means bonds the cutpiece, which is composed of the other members of the first sheetmaterial 1, to a substrate W with the first adhesive interposedtherebetween, while it removes the second release film. In the bondingprocess as shown in FIG. 11B, a press roller 305 and a guide roller 3051are used to press the first sheet material 1 against the surface of thesubstrate W so that it can be bonded to the surface. The pressure andmovement of the press roller 305 are controlled by the first controlmeans. The delamination mechanism has a sharp-ended knife edge N1 and isconfigured so that the second release film H1 can be peeled off bytaking up the second release film H1 with the knife edge N1 and turningthe direction of the feeding and that the first sheet material 1 peeledoff from the second release film H1 can be fed to the surface of thesubstrate W. This process may include applying a tension of 150 N/m to1,000 N/m to the second release film and/or pressing the first sheetmaterial 1 against the surface of the substrate W within 3 seconds fromthe removal of the second release film H1, so that the first sheetmaterial 1 can be bonded with improved accuracy. If the tension is lessthan 150 N/m, the position from which the first sheet material 1 is fedmay be unstable. If it is more than 1,000 N/m, the second release filmH1 may be elongated to break. If the time until the pressing is longerthan 3 seconds, the end portion of the first sheet material 1 peeled offfrom the second release film H1 may be bent so that folding or airbubbles may occur. The bonding mechanism includes the press roller 305and the guide roller 3051 opposed thereto. The guide roller 3051includes a rubber roller driven by a motor, and immediately above theguide roller 3051, the press roller 305 comprising a metallic rollerdriven by a motor is provided movable upward and downward. When thesubstrate W is fed to the bonding position, the press roller 305 iselevated to a position higher than the upper surface so that the spacebetween the rollers is widened. Alternatively, the guide roller 3051 andthe press roller 305 may each be a rubber roller or a metallic roller.The substrate W has been previously cleaned and stored. It is placed onthe feeding mechanism by suction feeding means 306, which is alsocontrolled by the first control means.

Second Manufacturing Unit

In the second manufacturing unit for the respective steps, the secondmounting means, the second feeding means, the third release filmremoving means, the second defect inspecting means, the fourth releasefilm bonding means, the second cutting means, and the second bondingmeans are the same as the corresponding means of the first manufacturingunit, and therefore, a description thereof is omitted.

The substrate W1 processed in the first manufacturing unit is fed to thesecond manufacturing unit. The substrate W1 is turned upside down in thefeeding process or in the second manufacturing unit. The turning means(not shown) is configured to suck the substrate W1 from the upper sideby sucking means, lift it, turn it upside down, and place it the feedingmechanism again. The second control means functions to control thisprocess. In another embodiment, the second manufacturing unit may beconfigured not to turn it upside down. In this case, the secondmanufacturing unit is configured to perform each step with the secondsheet material 2 being held in a reversed state (with the release filmfacing upward), unlike the usual state, and to bond the second opticalmember to the lower side of the substrate W1. When the bonding isperformed so that the second optical member can be in 90° relation(crossed Nicol relation) to the first optical member, the substrate W1is turned by 90°, and then the second optical member is bonded thereto.

The first and second control means control the means for the respectivesteps so that they can be synchronized. The timing of the operation ofeach means is calculated by a method using sensors placed at specificlocations or by a method of detecting the rotating part of the feedingmechanism with a rotary encoder or the like. The first and secondcontrol means may be implemented in cooperation with software programsand hardware resources such as CPU and memories. In this case, programsoftware, procedures, various settings, and so on are previously storedin memories. Private circuits, firmware, or the like may also be usedfor the implementation.

Other Embodiments

In the above embodiments, defect-containing sheet materials are bondedto temporary plate units and collected. Alternatively, such materialsmay be bonded to a belt-shaped separator so that they can be collectedin the form of a roll.

The defect inspection may be performed using known defect inspectionmethods. Examples of defect inspection methods include inspection withautomatic inspection equipment and visual inspection by a checker.Automatic inspection equipment includes a system to automaticallyinspect defects (also referred to as flaws) in the sheet material, whichperforms a process including applying light to the material, capturingthe reflected-light image or the transmitted-light image through animaging unit such as a line sensor or a two-dimensional TV camera, anddetecting defects based on the captured image data. The image data arealso captured through a polarizing filter placed for inspection in theoptical path between the light source and the imaging unit. In general,the polarization axis (e.g., polarized light absorption axis) of thepolarizing filter for inspection is placed so as to be orthogonal(crossed-Nicol) to the polarization axis (e.g., polarized lightabsorption axis) of the polarizing plate as the test object. In thecrossed-Nicol configuration, no defect allows a full black image to beinput from the imaging unit, while any defect portion is detected asbeing not black (observed as a bright spot). Therefore, if anappropriate threshold is determined, defects can be detected. In suchbright spot detection, defects such as surface deposits and internalforeign matter are detected as bright spots. Besides the bright spotdetection, a method including capturing the transmitted-light image ofthe object with CCD and analyzing the image to detect foreign matter isalso applicable. In addition, a method including capturing thereflected-light image of the object with CCD and analyzing the image todetect foreign matter deposited on the surface is also applicable.

The cutting step has been described with respect to the method ofcutting the members of the sheet material other than the release film(half cutting method). In an embodiment of the invention, however, thecutting step is not limited to such a cutting method. Other modes of thecutting step and the bonding step are described below with reference toFIGS. 15 and 16.

Full Cutting Method Using Carrier Film

A full cutting method using a carrier film is described with referenceto FIG. 15. A roll of a carrier film is placed at a location where thesheet material is fed. For example, the carrier film is an adhesive tapeor an adhesive tape. First, the carrier film is fed from the roll andbonded to the surface protecting film of the sheet material, while it ispressed with a roll. Subsequently, all the members of the sheet materialbeing fed together with the carrier film are cut, without cutting thecarrier film. An adhesive tape is then fed from a roll thereof andbonded to the release film, while it is pressed with a roll. Theadhesive tape is taken up so that the release film can be peeled off.Subsequently, the same method as shown in FIG. 11B is used in which thesheet material is bonded to the substrate using a press roller and aguide roller, while the carrier film is peeled off using a knife edgepart. Alternatively, the carrier film may be peeled off, after the sheetmaterial is bonded to the substrate.

Half Cutting Method with Surface Protecting Film Left Uncut

A method of cutting the members of the sheet material other than thesurface protecting film is described with reference to FIG. 16. First,while the surface protecting film is left uncut, the other members ofthe sheet material being fed are cut. Subsequently, the same peelingstep as shown in FIG. 15 is used in which an adhesive tape is fed from aroll thereof and bonded to the release film, while it is pressed with aroll, and the adhesive tape is taken up so that the release film can bepeeled off. The same method as shown in FIG. 11B is then used in whichthe sheet material is bonded to the substrate using a press roller and aguide roller. The surface protecting film is then cut by cutting means.

Optical Member

Some examples have been described with respect to the polarizer used toform the first and second optical members and a polarizer protectingfilm used on one or both sides of the polarizer. However, generalexamples include the materials described below. A polarizer and a filmor films to be placed on one or both sides of the polarizer may beselected from the examples so that they can have differentfeed-direction elastic moduli and different dimensional change rates,and a combination thereof may be used.

Polarizer

The processes of dyeing, crosslinking and stretching a polyvinyl alcoholfilm are not necessarily independently performed and may be performed atthe same time or in any order. The polyvinyl alcohol film may besubjected to a swelling process before use. The process may generallyinclude the steps of immersing the polyvinyl alcohol film in a solutioncontaining iodine or a dichroic dye so that the film is dyed with theiodine or the dichroic dye being adsorbed thereto, then washing thefilm, uniaxially stretching the film to 3 to 7 times in a solutioncontaining boric acid, borax or the like, and then drying the film. Itis particularly preferred that the step of stretching the film in asolution containing iodine or a dichroic dye should be followed by thesteps of further stretching the film in a solution containing boricacid, borax or the like (two-stage stretching) and then drying the film,so that the iodine can be highly oriented to provide good polarizingproperties.

For example, the polyvinyl alcohol polymer may be a polymer produced bypolymerizing vinyl acetate and then saponifying the polymer or acopolymer produced by copolymerizing vinyl acetate with a small amountof a copolymerizable monomer such as an unsaturated carboxylic acid, anunsaturated sulfonic acid, or a cationic monomer. The averagepolymerization degree of the polyvinyl alcohol polymer is preferably,but not limited to, 1,000 or more, more preferably from 2,000 to 5,000.The saponification degree of the polyvinyl alcohol polymer is preferably85% by mole or more, more preferably from 98 to 100% by mole.

The thickness of the produced polarizer is generally, but not limitedto, from 5 to 80 μm. The thickness of the polarizer may be controlled byany conventional method such as tentering, roll stretching, or rolling.

As a non-limiting example, the polarizer and a polarizer-protectingtransparent film serving as a protective layer may be bonded to eachother with a bonding adhesive such as a bonding adhesive including avinyl alcohol polymer or a bonding adhesive including a vinyl alcoholpolymer and a water-soluble crosslinking agent therefor such as boricacid, borax, glutaraldehyde, melamine, or oxalic acid. The bondingadhesive layer may be formed by applying and drying an aqueous solutionlayer. In the process of preparing the aqueous solution, if necessary,any other additive or a catalyst such as an acid may also be added.

Polarizer Protecting Film

Any appropriate transparent film may be used as the polarizer protectingfilm to be placed one or both sides of the polarizer. For example,thermoplastic reins with a high level of transparency, mechanicalstrength, thermal stability, water-blocking performance, isotropy, orthe like may be used. Examples of such thermoplastic resins includecellulose resins such as triacetylcellulose, polyester resins,polyethersulfone resins, polysulfone resins, polycarbonate resins,polyamide resins, polyimide resins, polyolefin resins, (meth)acrylicresins, cyclic polyolefin resins (norbornene resins), polyarylateresins, polystyrene resins, polyvinyl alcohol resins, and any blendthereof. While a transparent protective film may be bonded to one sideof the polarizer with an adhesive layer, a thermosetting resin or anultraviolet-curable resin such as a (meth)acrylic, urethane, acrylicurethane, epoxy, or silicone resin may be used to form a transparentprotective film on the other side of the polarizer. The transparentprotective film may contain any one or more appropriate additives.Examples of such an additive include an ultraviolet absorbing agent, anantioxidant, a lubricant, a plasticizer, a release agent, ananti-discoloration agent, a flame retardant, a nucleating agent, anantistatic agent, a pigment, and a colorant. The content of thethermoplastic resin in the transparent protective film is preferablyfrom 50 to 100% by weight, more preferably from 50 to 99% by weight,even more preferably from 60 to 98% by weight, in particular, preferablyfrom 70 to 97% by weight. If the content of the thermoplastic resin inthe transparent protective film is less than 50% by weight, hightransparency and other properties inherent in the thermoplastic resinmay be insufficiently exhibited. Amorphous PO films, cycloolefin polymer(COP) films, Arton films (manufactured by JSR Corporation), Zeonor films(manufactured by Zeon Corporation), and so on may also be used.

The polymer film described in JP-A No. 2001-343529 (WO01/37007) may alsobe used, for example, which comprises a resin composition containing (A)a thermoplastic resin having a substituted and/or unsubstituted imidegroup in the side chain and (B) a thermoplastic resin having asubstituted and/or unsubstituted phenyl and nitrile groups in the sidechain. Specifically, the film comprises a resin composition containingan alternating copolymer of isobutylene and N-methylmaleimide and anacrylonitrile-styrene copolymer. The film may be produced bymixing-extrusion of the resin composition. These films have a low levelof retardation and photoelastic coefficient and thus can preventpolarizing plates from having defects such as strain-induced unevenness.They also have low water-vapor permeability and thus have high humidityresistance.

The thickness of the transparent protective film is generally from about1 to about 500 μm, in particular, preferably from 1 to 300 μm, morepreferably from 5 to 200 μm, in view of strength, workability such ashandleability, thin layer formability, or the like, while it may bedetermined as needed. A transparent protective film with a thickness of5 to 150 μm is particularly preferred.

For practical use, the optical member may also have a multilayeredstructure in which various optical layers are laminated. Examples ofsuch optical layers include, but are not limited to, layers formed byperforming hard coating treatment, antireflection treatment, or surfacetreatment for anti-sticking, diffusion or antiglare purpose on thetransparent protective film surface to which no polarizer will be bonded(the surface on which the bonding adhesive coating layer is notprovided), and oriented liquid crystal layers for viewing anglecompensation or other purposes. An optical film(s) for use in forming aliquid crystal display or the like, such as a reflector, a transflector,a retardation plate (including a wavelength plate (λ plate) such as ahalf or quarter wavelength plate), or a viewing angle compensation filmmay also be used in the form of a layer or a laminate of two or morelayers.

Retardation Plate

An example of the optical film to be placed on the polarizer includes aretardation plate. Examples of the retardation plate includebirefringent films produced by uniaxially or biaxially stretchingpolymer materials, oriented liquid crystal polymer films, and orientedliquid crystal polymer layers supported on films. The stretching processmay be typically performed by roll stretching, long-gap stretching,tenter stretching, or tubular stretching. Uniaxial stretching isgenerally performed to a stretch ratio of about 1.1 to about 3. Thethickness of the retardation plate is generally, but not limited to,from 10 to 200 μm, preferably from 20 to 100 μm.

Examples of the polymer materials include polyvinyl alcohol, polyvinylbutyral, poly(methyl vinyl ether), poly(hydroxyethyl acrylate),hydroxyethyl cellulose, hydroxypropyl cellulose, methylcellulose,polycarbonate, polyarylate, polysulfone, polyethylene terephthalate,polyethylene naphthalate, polyethersulfone, polyphenylene sulfide,polyphenylene oxide, polyallylsulfone, polyvinyl alcohol, polyamide,polyimide, polyolefin, polyvinyl chloride, cellulose polymers, andvarious types of binary or ternary copolymers thereof, graft copolymersthereof, and any blend thereof. Any of these polymer materials may beformed into an oriented product (a stretched film) by stretching or thelike.

Viewing Angle Compensation Film

Another example of the optical film to be placed on the polarizerincludes a viewing angle compensation film. The viewing anglecompensation film is for expanding the viewing angle so that images canbe relatively clearly viewed even when the screen of a liquid crystaldisplay is viewed from directions not perpendicular but somewhat obliqueto the screen. Examples of such a viewing angle compensation retardationplate include a retardation film, an oriented film of a liquid crystalpolymer or the like, and an oriented layer of a liquid crystal polymeror the like supported on a transparent substrate. General retardationplates are produced with a polymer film that is uniaxially stretched inthe in-plane direction and has birefringence. On the other hand,retardation plates for use as the viewing angle compensation film areproduced with a bi-directionally stretched film such as a polymer filmthat is biaxially stretched in the in-plane direction and hasbirefringence, a polymer film that is uniaxially stretched in thein-plane direction and also stretched in the thickness direction so thatit has a controlled refractive index in the thickness direction and hasbirefringence, and an obliquely oriented film. Examples of the obliquelyoriented film include a film produced by a process including bonding aheat-shrinkable film to a polymer film and stretching and/or shrinkingthe polymer film under the action of the heat-shrinkage force, and anobliquely-oriented liquid crystal polymer film. The raw material polymerfor the retardation plate may be the same as the polymer described abovefor the retardation plate, and any appropriate polymer may be useddepending on the purpose such as prevention of coloration caused bychanges in viewing angle based on the retardation of a liquid crystalcell and expansion of the viewing angle at which good visibility isachieved.

In order to expand the viewing angle at which good visibility isachieved, an optical compensation retardation plate is preferably used,which includes a triacetylcellulose film and an optically-anisotropiclayer of an oriented liquid crystal polymer, specifically anobliquely-oriented discotic liquid crystal polymer layer, supported onthe film.

Brightness Enhancement Film

A laminate of a polarizing plate and a brightness enhancement film isgenerally placed on the back side of a liquid crystal cell, when used.The brightness enhancement film exhibits the property that when light isincident on it from a backlight of a liquid crystal display or the likeor when natural light is reflected from the back side and incident onit, it reflects linearly polarized light with a specific polarizationaxis or reflects circularly polarized light in a specific direction andtransmits the other part of the light. When light from a light sourcesuch as a backlight is incident on a laminate of a polarizing plate anda brightness enhancement film, transmitted light in a specificpolarization state is produced, and light in the state other than thespecific polarization state is not transmitted but reflected. The lightreflected from the surface of the brightness enhancement film may bereversed by a reflective layer or the like provided behind thebrightness enhancement film and allowed to reenter the brightnessenhancement film so that the light can be entirely or partiallytransmitted in the specific polarization state. In this case, thequantity of the light transmitted through the brightness enhancementfilm can be increased, and polarized light, which is less likely to beabsorbed by the polarizer, can be supplied so that the brightness can beenhanced by increasing the quantity of the light available at a liquidcrystal image display or the like.

Examples of the brightness enhancement film that may be used include afilm having the property of transmitting linearly polarized light with aspecific polarization axis and reflecting the other type of light, suchas a dielectric multilayer thin film or a multilayer laminate of thinfilms different in refractive index anisotropy, and a film having theproperty of reflecting one of clockwise circularly polarized light andcounterclockwise circularly polarized light and transmitting the other,such as an oriented cholesteric liquid crystal polymer film or anoriented cholesteric liquid crystal layer supported on a film substrate.

Adhesive

In an embodiment of the invention, the polarizing plate or the opticalmember is provided with an adhesive layer for bonding it to anothercomponent such as a liquid crystal cell. The adhesive layer may beformed of any appropriate adhesive such as an acrylic adhesive accordingto conventional techniques. The adhesive layer preferably has lowmoisture absorption coefficient and high heat resistance, in order toprevent moisture absorption-induced foaming or peeling, to preventoptical property degradation due to a thermal expansion difference orthe like, to prevent warping of a liquid crystal cell, and to form animage display with high quality and high durability. The adhesive layermay also contain fine particles so as to have light diffusingproperties. The adhesive layer may be provided as needed on a necessarysurface. Concerning a polarizing plate comprising a polarizer and apolarizer protecting film layer, for example, an adhesive layer may beprovided as needed on one or both sides of the polarizer protectinglayer.

Release Film

The exposed surface of the adhesive layer may be temporarily coveredwith a release film (it may also called “separator”) for antifouling orthe like until it is put to use. This can prevent contact with theadhesive layer during usual handling. A conventional appropriateseparator may be used, such as an appropriate thin leave including aplastic film, a rubber sheet, a paper sheet, a cloth, a nonwoven fabric,a net, a foam sheet, a metal leaf, or a laminate thereof, which isoptionally coated with any appropriate release agent such as a silicone,long-chain alkyl or fluoride release agent, or molybdenum sulfide.

Surface Protecting Member

A surface protecting member may be provided on the opposite side of theoptical member from the side where the separator is provided. A surfaceprotecting film may be formed as the surface protecting member through aweak adhesive. The main purpose thereof is anti-scratch, antifouling, orthe like. For example, the surface protecting film may be a single layerof a plastic film or a laminate of plastic film layers. Examples of thesurface protecting member include an appropriate thin leave such as aplastic film, a rubber sheet, a paper sheet, a cloth, a nonwoven fabric,a net, a foam sheet, a metal leaf, or a laminate thereof, which isoptionally coated with any appropriate release agent such as a silicone,long-chain alkyl or fluoride release agent, or molybdenum sulfide.

In an embodiment of the invention, an ultraviolet absorbing capabilitymay be imparted to the polarizer, the polarizer protecting film, or anyother film such as the surface protecting film or the release film, oreach layer such as the adhesive, for example, by treatment with anultraviolet-absorbing agent such as a salicylate ester compound, abenzophenol compound, a benzotriazole compound, a cyanoacrylatecompound, or a nickel complex salt compound.

Optical Image Display

In an embodiment of the invention, the optical member is preferably usedto form an image display such as a liquid crystal display, an organicelectroluminescence display (organic EL display) or a plasma displaypanel (PDP).

In an embodiment of the invention, the optical member is preferably usedto form any of various devices such as liquid crystal displays. Liquidcrystal displays may be formed according to conventional techniques.Specifically, a liquid crystal display may be typically formed byassembling a liquid crystal cell and optical films, and optionalcomponents such as a lighting system and by incorporating a drivingcircuit according to conventional techniques, except that the opticalfilm is used according to the invention. Any type of liquid crystal cellsuch as TN type, STN type or n type may be used.

EXAMPLES

Sheet materials including optical members having different filmstructures were each bonded to a substrate using the manufacturingmethod of Embodiment 4 described above. The results are shown in Tables2 and 3. In addition, a 38 μm thick polyethylene terephthalate film(surface protecting film) is provided on the TAC1- or TAC2-side surfacelayer of the sheet material with an about 20 μm thick acrylic bondingadhesive interposed therebetween, and a 25 μm thick polyethyleneterephthalate film (release film) is provided on the α-film- orstretched PVA-side of the sheet material with an about 20 μm thickacrylic bonding adhesive interposed therebetween.

FIG. 17 shows a method for measuring the bonding accuracy. A sheetmaterial B is bonded to a substrate A according to a bonding directionk. At each of positions P1 and P2 of the substrate A, the distancebetween the end faces of the substrate and the optical member ismeasured. P1 and P2 are each located 20 mm from each widthwise end faceof the substrate A. The bonding position is set in advance, and the setpoint is achieved, if the bonding is perfect. Each set point is 5.5 mm.The bonding accuracy is obtained by subtracting the measured value fromthe set point. If the calculated value is negative, it means thatrelative to the substrate A, the bonded sheet material B deviates in adirection opposite to the bonding direction k. If the calculated valueis positive, it means that relative to the substrate A, the bonded sheetmaterial B deviates in the bonding direction k. In this case, the sheetmaterial B includes the optical member and the surface protecting film.

In the evaluation of peeling on a roll, the sheet material after halfcutting was turned back at an angle of 180° and a velocity of 5 m/minuteon a roll with a diameter of 75 mm, and how the sheet material peeledfrom the release film was observed at the time of the turning. A peel of10 mm or more, a peel of less than 10 mm, and no peel were expressed bythe marks “x,” “Δ” and “◯,” respectively. The elastic modulus, thedimensional change rate and the amount of curling were also measured bythe methods described above.

TABLE 2 MD Structure of Dimensional Elastic curling Amount of Structureof α-film third change rate modulus state of MD curing first and secondlayer of Thickness of α-film of α-film sheet of sheet Bonding accuracylayers of optical of α-film (%, 70° C.) (MPa) material material (mm)Peeling EXAMPLES optical member member (μm) MD MD (note 2) (mm) P1 P2 onroll 1 Structure TAC1: KC4UY 40 0.2 2,500 Minus 20 0.3 0.0 ∘(TAC2/stretched manufactured PVA/α) by Konica Minolta 2 Structure TAC3:KC-4FR 40 0.8 1,800 Minus 30 −0.3 −0.4 ∘ (TAC2/stretched manufacturedPVA/α) by Konica Minolta 3 Structure Norbornene- 70 0.4 1,200 Minus 40−0.3 −0.2 ∘ (TAC2/stretched based (Zeonor PVA/α) Film Δnd = 65 nm,manufactured by ZEON CORPORATION) 4 Structure Norbornene- 50 1.0 1,000Minus 50 −0.4 −0.5 ∘ (TAC2/stretched based (Arton PVA/α) (note 1)manufactured by JSR Corporation) 5 Structure Acrylic 1 30 0.6 1,500Minus 55 −0.3 −0.5 ∘ (TAC2/stretched (resin PVA/α) disclosed in Example1 of JP-A No. 2000-230016) 6 Structure Absent (two- — — — Minus 80 −0.7−0.8 ∘ (TAC2/stretched layer PVA) structure) 7 Structure Absent (two- —— — Minus 120 −1.5 −2.1 ∘ (TAC1/stretched layer PVA) structure)Comparative Structure TAC2: TD-80UL 80 0.1 1,500 Zero 0 x x Δ example 1(TAC2/stretched manufactured PVA/α) by Fujifilm Corporation ComparativeStructure TAC4: WVBZ 80 — 2,000 Plus 20 x x x example 2 (TAC2/stretchedFilm PVA/α) manufactured by Fujifilm Corporation (Note 1) Arton is aproduct obtained by stretching an Arton film to 1.5 times in thefilm-feed direction at a temperature of 155° C. or less. The releasefilm is provided on the α-film or the stretched PVA with an adhesiveinterposed therebetween. The surface protecting film is provided on TAC2or TAC1 with an adhesive interposed therebetween. (Note 2) When thesheet material curls so that the release film is facing inward, the MDcurling state is indicated as “minus.” When the sheet material curls sothat the release film is facing outward, the MD curling state isindicated as “plus.”

TABLE 3 Structure of Structure of Dimensional Elastic MD curling Amountof first and α-film third change rate modulus of state of MD curingsecond layers layer of Thickness of α-film α-film sheet of sheet Bondingaccuracy of optical optical of α-film (%, 70° C.) (MPa) materialmaterial (mm) Peeling EXAMPLES member member (μm) MD MD (note 2) (mm) P1P2 on roll 8 Structure Absent (two- — — — Minus 120 −1.7 −2.0 ∘(PET/stretched layer PVA) structure) 9 Structure (PET/ TAC1: KC4UY 400.2 2,500 Minus 10 −0.1 −0.1 ∘ stretched manufactured PVA/α) by KonicaMinolta 10 Structure (PET/ TAC2: TD- 80 0.1 1,500 Minus 20 −0.2 −0.4 ∘stretched 80UL PVA/α) manufactured by Fujifilm Corporation 11 Structure(PET/ TAC3: KC-4FR 40 0.8 1,800 Minus 10 −0.2 −0.2 ∘ stretchedmanufactured PVA/α) by Konica Minolta 12 Structure (PET/ TAC4: WVBZ 80 —2,000 Minus 20 −0.3 −0.5 ∘ stretched Film PVA/α) manufactured byFujifilm Corporation 13 Structure (PET/ Norbornene- 70 0.4 1,200 Minus15 −0.1 −0.3 ∘ stretched based PVA/α) (Zeonor Film Δnd = 65 nm,manufactured by ZEON CORPORATION) 14 Structure (PET/ Norbornene- 50 1.01,000 Minus 10 0.0 −0.2 ∘ stretched based (Arton PVA/α) (note 1)manufactured by JSR Corporation) 15 Structure (PET/ Biaxially- 20 —1,900 Minus 20 −0.3 −0.1 ∘ stretched stretched PP PVA/α) 16 Structure(PET/ Acrylic 1 30 0.6 1,500 Minus 15 0.0 −0.2 ∘ stretched (resin PVA/α)disclosed in Example 1 of JP-A No. 2000-230016) (Note 1) Arton is aproduct obtained by stretching an Arton film to 1.5 times in thefilm-feed direction at a temperature of 155° C. or less. The releasefilm is provided on the α-film or the stretched PVA with an adhesiveinterposed therebetween. The surface protecting film is provided on PETor TAC1 with an adhesive interposed therebetween. PET used was T100 (38μm in thickness) manufactured by Mitsubishi Polyester Film Inc. (Note 2)When the sheet material curls so that the release film is facing inward,the MD curling state is indicated as “minus.” When the sheet materialcurls so that the release film is facing outward, the MD curling stateis indicated as “plus.”

The results of Tables 2 and 3 show that the sheet materials of Examples1 to 16 each curls in its longitudinal direction so that the releasefilm is facing inward (minus curling) and that peeling was not observedon the roll in each of the sheet materials of Examples 1 to 16. When thesheet material having the structure shown in Table 2 or 3 has a curlingamount of 5 mm to 100 mm, the bonding accuracy is also good. InComparative Examples 1 and 2, however, peeling was observed on the roll,and a bonding failure occurred.

The invention claimed is:
 1. A material roll comprising a roll of acontinuous sheet material, comprising: an optical member comprising apolarizer; and a release film provided on one side of the optical memberwith an adhesive interposed therebetween, and a surface protectingmember provided on another side of the optical member; wherein theoptical member is constructed of materials that cause the continuoussheet material to curl in the longitudinal direction of the continuoussheet material when no external force is applied in such a way that therelease film is facing inward, and the continuous sheet material is foruse in a process comprising half cutting and bonding the optical memberto a substrate with the adhesive interposed therebetween to form anoptical display unit; wherein the half cutting is a process comprisingcutting the member of the continuous sheet material while leaving therelease film or the surface protecting member uncut or a processcomprising bonding a carrier film to the continuous sheet material andcutting the continuous sheet material while leaving the carrier filmuncut; wherein the material roll is wound so that the release film isplaced facing inward from a center core of the roll and the opticalmember is placed facing outward from the center core of the roll;wherein a cut sample of the sheet material has a curling amount of 5 mmto 100 mm, when it is placed on a flat surface so that it can curl tobecome convex downwardly, wherein the sample is obtained by cutting thesheet material in a length of 29.7 cm parallel to the longitudinaldirection and in a width of 21.0 cm perpendicular to the longitudinaldirection, and the curling amount is the height of an edge of the samplefrom the flat surface.
 2. The material roll of claim 1, wherein theoptical member comprises a first film provided on one side of thepolarizer, a second film provided on another side of the polarizer, andan adhesive provided on the second film, wherein the release film isprovided on the second film with the adhesive interposed therebetween,and the longitudinal dimensional change rate of the first film is lowerthan the longitudinal dimensional change rate of the second film.